A transmitter generates radio signals required for communications. It consists of a data source, modulator and power amplifier (PA), as shown in FIG. 1. The modulator varies the amplitude, phase, and/or frequency of a carrier signal depending on the communication method selected.
FIG. 2 shows a detailed diagram of a standard radio transmitter architecture. It uses two mixers (202, 204) to generate the modulated signal and a third mixer (206) to shift the signal to radio frequency for propagation using electromagnetic waves. It relies on high-Q filters (208, 210) that are difficult to integrate but are needed to limit broadband noise and spurs. This architecture typically operates at high current levels, which limits its usefulness in portable radio equipment. It would therefore be advantageous to have a more efficient radio transmitter architecture that is more suitable for use in portable radio equipment.